Simian hemorrhagic fever (SHF) is an enzootic disease in feral E. patas monkeys (10%). The agent has been found occasionally in other feral African monkeys. The disease among Asian Macaque monkeys is caused by a laboratory accident, usually transmitted by contaminated needles. SHF in patas monkeys can be mechanically transmitted by insect vectors. The virus from patas monkeys has not been isolated in tissue culture. The chronic disease in patas monkeys causes immune-complexes in the animal's kidneys and is vertically transmitted. Treatment was not successful when poly IC-poly-L-lysine complex was given to chronically infected patas monkeys.